Children’s bicycles often feature bright colours or are in some way colourful. You’ll find few as black as the JEFFSY PRIMUS 24. But kids’ bikes are rarely as closely related to their grown-up gravity focused counterparts as the YT.

YT JEFFSY PRIMUS 24 | Weight: 12.5 kg | Size recommendation: 135–150 cm | Price: € 2.199 | Manufacturer-website

By the way: In addition to the Jeffsy, we have tested a lot of other children’s bikes and other concepts for the bikers of tomorrow. You can find all the findings in our detailed kids bike buyers’ guide.

With 24″ wheels, the JEFFSY PRIMUS we tested rolls on the smaller of two wheel size options, though that doesn’t stop it from making a big impression. The YT bears the name of its grown-up counterpart with its head held high. Hardly any kids bike craves dirt as much as this one. It’s not just its discrete black colour scheme that makes it scream how much it can’t wait to play with its big siblings. The air suspension of the JEFFSY PRIMUS offers 130 mm travel front and rear and is optimised for the weights of young shredders. Thanks to the clear pictograms, finding the right suspension setup should be easy and is nice way of introducing kids to the more technical aspects of bikes. The YT rolls on super aggressive tires from MAXXIS whose strengths lie less in rolling speed and more in braking and cornering grip on the trail. Things continue with solid components for the saddle, pedals, powerful brakes and adjustable brake levers, creating a child-friendly cockpit. However, we advise swapping the shifter and the brake, putting the shifter first. This arrangement makes it easier to brake with just one finger and your young shredder can get used to doing it the right way from the start. The standard seat and chainstay protector offers adequate protection from chain during landings and impacts. All that’s missing on the JEFFSY PRIMUS 24 is a dropper post, which would complete the picture of a full-fledged miniature Jeffsy. This does come as standard on the € 100 more expensive 26″ model. Both rely on a standard bottom bracket, making for a wide stance, especially on the smaller model.

YT are one of the few brands that spec a thinner handlebar and thus also skinnier grips that are easier for kids to grasp.
The lever reach of the brakes can be adjusted without tools.
The tires feature an aggressive tread pattern, offering plenty of grip in rough off-road terrain. That’s exactly where the YT belongs.
Suspension fork
The Manitou fork on the YT has a table that helps you and your kid find the right setup.

The YT JEFFSY PRIMUS 24 presents a clear departure from the usually colourful world of kids’ bikes. Instead, it’s a fully-fledged trail toy with a lot of child-friendly components. Thanks to its gravity oriented spec and stealth looks, we know exactly where it wants to take young shredders: the descents!


  • coherent trail and bike park concept for kids
  • high-performance components for shredding
  • in no way inferior to the Jeffsy for adults


  • dropper seat post only standard on the 26

Find more information here:

11 exciting concepts at a glance

You can get an overview of this comparison test here: kids bike buyer’s guide – 11 exciting concepts at a glance.

All kids bikes in this group test: Tout Terrain Singletrailer Trailer (Click for review) | Shotgun Pro MTB child seat (Click for review) | Leg&go balance bike (Click for review) | Mondraker Grommy-E-balance bike (Click for review) | Early Rider Hellion 16-kids bike (Click for review) | Woom OFF 5- / OFF AIR 5 kids bike(Click for review) | Woom UP 5 kids ebike (Click for review) | Ben-E-Bike TWENTYFOUR-SIX E-POWER FS kids mountain bike (Click for review) | SCOTT Ransom 600 kids mountain bike (Click for review) | VPACE MORITZ26 kids mountain bike (Click for review) | YT JEFFSY PRIMUS 24 kids mountain bike

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Words: Moritz Geisreiter, Peter Walker, Felix Stix Photos: Peter Walker, Daniel Geiger